linux-kernel - Re: [PATCH 2/3] jump_label: Provide static_key_slow_inc

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Message-ID: <20170419063918.3z2ndmmtn2xwrb6r@hirez.programming.kicks-ass.net>
Date:   Wed, 19 Apr 2017 08:39:18 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Steven Rostedt <rostedt@...dmis.org>, jbaron@...mai.com,
        mingo@...nel.org, bigeasy@...utronix.de,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] jump_label: Provide static_key_slow_inc_nohp()

On Tue, Apr 18, 2017 at 10:50:43PM +0200, Thomas Gleixner wrote:
> On Tue, 18 Apr 2017, Peter Zijlstra wrote:
> > On Tue, Apr 18, 2017 at 12:46:29PM -0400, Steven Rostedt wrote:
> > > On Tue, 18 Apr 2017 15:03:50 +0200
> > > Peter Zijlstra <peterz@...radead.org> wrote:
> > > 
> > > > +++ b/kernel/padata.c
> > > > @@ -1008,11 +1008,10 @@ static struct padata_instance *padata_al
> > > >   *                         parallel workers.
> > > >   *
> > > >   * @wq: workqueue to use for the allocated padata instance
> > > > - *
> > > > - * Must be called from a get_online_cpus() protected region
> > > 
> > > Find the comment redundant?
> > 
> > Once there's code that enforces it? Yes. Nobody reads comments
> > ;-)
> 
> Nobody enables lockdep either .....

In the grand scheme of things, true. But there are more people running
with lockdep enabled than there are people writing code, of which there
are more than people reading relevant comments while writing code.
Therefore having the lockdep annotation is two orders better than a
comment ;-)

Also, I would argue that an "assert" at the start of a function is a
fairly readable 'comment' all by itself.

In any case, I don't care too much. But I typically remove such comments
when I stick a lockdep_assert_held() in.